According to the GlaxoSmithKline, or GSK, website, the three stripes in Aquafresh represent the three benefits of using the toothpaste, namely strong teeth, healthy gums and fresh breath. The three stripes make the toothpaste visually distinct.
According to SurvivinginJapan.com, the three stripes of the Aquafresh toothpaste represent a preventative benefit for oral health. The red, blue and white stripes are for preventing cavities, periodontitis and bad breath respectively. This description was found by an expert blogger and former columnist for The Japan Times in the Aquafresh toothpaste packaging in Japan. The Aquafresh triple protection variant was first introduced in 1981, according to Wikipedia. Bravis International notes that Aquafresh was the first toothpaste in the world to include fluorine to prevent tooth decay.